An inherent aspect of any two-dimensional (2D) sheet is that all
atoms in the material lie on the surface. This leads to a concept
of 2D crystals as a “canvas,” where different chemical groups or
“ink” on the surface can lead to a palette of distinct materials
properties. The most well-studied 2D crystal is graphene, a
one-atom-thick sheet of carbon atoms arranged in a honeycomb
lattice. Although graphene's superlative materials properties and
novel physical phenomena have led to a variety of applications (1),
better tunability of these properties is still required. Toward
this end, hydrogenated graphene (graphane) was predicted to have a
wide band gap and exhibit magnetic order (2–4), in contrast to
graphene, which is (semi)metallic and diamagnetic. The chemical
stability of graphene makes hydrogenation difficult to control, and
this has hampered efforts to tune its electronic or magnetic
properties. On page 437 of this issue, González-Herrero et al....